1. Field of the Invention
The present invention relates to double-lift dobbies of the HATTERSELY type, intended for forming the shed on weaving machines.
2. History of Related Art
It is known that, in the dobbies of the HATTERSLEY type, each of the heddle frames of the weaving machine is connected to a rocking lever which is equipped with a swinging lever of which each of the end supports a coupling member in the form of a drawing hook. Each hook is capable of coming into engagement with a traction member constituted by a reciprocating knife adapted to displace the swinging lever and its heddle frame as a function of the weaving program of the system. In the conventional construction, the system acts on the drawing hooks which are displaced so as either to cooperate with the corresponding traction member or to avoid it.
To operate dobbies of this type in a more supple manner to attain higher operational speeds, it has been proposed, particularly in document DE-A-3 419 719 (KAISER), to mount the swinging lever, no longer directly on the end of the rocking lever connected to the heddle frame, but on a connecting rod connected to the rocking lever.
For the coupling members carried by each swinging lever to be abe to cooperate reliably with the knifes or other traction members, it is, of course, necessary that the intermediate connecting rod which supports the swinging lever be suitably guided in a longitudinal direction. However, it should be observed that such guiding is particularly delicate to ensure due to the tacking or loose zig-zag displacement of the connecting rod generated by the lateral offset of the pivot axis of the rocking lever to which the connecting rod is coupled.
In document DE-A-3 419 719 (KAISER) mentioned above, the end of the connecting rod extends beyond the pivot of the swinging lever and it is at this end that longitudinal guiding is effected. It will be understood that the tacking movement mentioned above makes it necessary to arrange a larger operational clearance, which clearance involves effects of friction which generate detrimental vibrations; furthermore, guiding by friction wears the contact surfaces in contact and heat is created which is detrimental to the correct functioning of the assembly.
It is a particular object of the present invention to overcome these drawbacks.